This invention relates to new and useful improvements in dust seals for gyratory rock crushers.
Effective dust seals for cone or gyratory-type rock crushers have been extremely difficult to achieve. The internal working parts (bearings, gears, shafts, oil pumps, and lubricating oil) must be protected from both rock dust developed during crushing and other contaminants, otherwise the best machines become too costly to maintain. No matter how good the crusher may be, if rock dust cannot be excluded, the machine is not viable.
Certain mechanisms using spinning labyrinth seals, such as in U.S. Pat. No. 3,118,623, are very effective for excluding dust, but such machines are restricted to smaller sizes because of the very high costs, speed limitations, and inadequate load carrying capacities of larger roller thrust bearings. In the larger sizes which are required to produce crushed rock in the capacities that today's and future markets demand, bigger crushers are essential.
Flexible seals have also been used, such as shown in U.S. Pat. Nos. 2,224,542, 2,832,547 and 4,192,472. Such seals comprise frusto-conical members secured between the crusher head and head support and can be designed for the larger type crusher. In view of the violent action of the crusher head, however, such flexible seals have been found to be short-lived. Rubbing seals have also been used and have a structure wherein one part of the seal is stationary on the base frame and the other part is attached to the gyrating cone head. Such a seal exposes a substantial surface area in a continuously moving orbit to the crusher's center line. Very fine rock dust will adhere to this surface. As this surface moves inward, most of the dust will be rubbed off but some will succeed in passing between the sealing surfaces. Over a period of time, dust accumulation reaches destructive levels. Efforts have also been made to use internal air pressure but such have not been satisfactory since it is difficult to push dust out and effective means have not been provided to prevent air from flowing into internal working parts such as into oil return drains.